A rotor blade for a wind-turbine can be tens of meters in length. One end of the blade, the blade root, generally has a circular cross-section for attaching to a pitch bearing. The blade root extends into a transition region, and beyond the transition region, the blade has an airfoil shape with curved surfaces, becoming progressively narrower and flatter, and tapering to a tip at the other extreme end of the blade. Such a blade is generally made of a rigid and relatively light material such as molded fiberglass. A blade with a length of about 95 m can weigh about 32,000 kg and can have a diameter of several meters at the root end. Because of its large dimensions and unwieldy shape, a lot of handling is involved in transporting a blade from a manufacturing site to a local storage site, from the storage site to a transport device, from the transport device to the wind-turbine site, etc. Because of its length, a blade is generally stored horizontally, for example on one of a stack of shelves that might be in an indoor hangar. To transfer a blade onto a transport device such as a ship or a railcar, a crane is generally used. For a crane to access a blade, it may be necessary to first fetch the blade from its shelf and to deposit it at an interim location such as a platform to allow crane access. To this end, a forklift truck or similar load transportation vehicle is usually used. For example, two forklifts can be used to hold and lift a blade, one at each end. Evidently, the drivers of the forklift trucks must exactly synchronize their movements, for example by line-of-sight, or verbally over a radio connection, in order to avoid damage to the blade. Alternatively, a third person might assist the drivers of the forklift trucks by observing and issuing commands.
In another approach, one forklift truck can be deployed to first transfer one end of the blade to an interim location, and then to ‘fetch’ the other end of the blade. It may be necessary to firmly secure the first end of the blade at the interim location to ensure it that does not move while the other blade end is being moved into place. Once the blade has been transferred to the interim location, it can be lifted, for example by crane, on to a transportation device such as a lorry or roll-on roll-off ship. In any case, these known procedures are very time-consuming, involve a lot of personnel and handling, and are not without risk of damage to the blade. An automated approach using one or more automated guided vehicles to fetch a blade and to carry it along a path defined by a guiding lane would require that blades are always stored at positions defined by guiding lanes, and any destination ferry or ship would also have to be equipped with such guiding lanes. Obviously, such a solution would be very complex and therefore costly and impracticable.